There is a great need for a totally implantable pressure transducer which can be read without repeatedly violating the scalp, skull or brain. We have done preliminary research on a device which would require a simple X-ray to read. The pressure sensor is a floppy bag inserted intraventricularly, intracerebrally or on the surface of the brain. The bag is filled with a non-radiopaque liquid and is connected via a tube to the surface of the skull where it enters a coiled capillary tube with standardized markings. Within the capillary tube there is a fluid-fluid interface where the nonradiopaque solution is in contact with a non-miscible radiopaque solution. The column of radiopaque solution continues through the capillary system until it ends in a gold plated nickel bellow which sits on the surface of the skull. The diameters of the tubes, the calibration of the bellows and the compliance of the floppy bag are such that one can directly read barometric compensated pressures by X-raying the coiled capillary tube and watching the displacement of the radiopaque marker. The device is simple, uses biologically safe materials and should be stable for many years. Phase 1 will consist of engineering and construction which should take 2 years. Phase 2 will be performed the 3rd and 4th year and will consist of laboratory testing in hydrocephalic puppies. Phase 3 will be the 5th year and will include preliminary human testing. Preliminary bench testing of the principals involved indicate this is a workable and practical approach to the problem of long term pressure measurement.